Such devices comprise a vertical cylindrical support tube supporting at its upper end the vise or the assembly platform and being guided for vertical movement directly or by means of a guide tube in a mounting by which the support tube can be attached to a work bench or the like. The mounting comprises two semicylindrical clamping shells which embrace the support tube and which can be clamped together to firmly hold the support tube in any desired vertical position. To this end the clamping shells are interconnected on one side i.e. along adjacent lateral edges by support means, and on the other side they can be clamped together by a clamping screw comprising a head which abuts against an outer surface of one shell and a nut with a handle abutting against an outer surface of the other shell. In order to facilitate the vertical adjustment of the support tube there is often provided a gas spring which exerts an upwardly directed force on the support tube. Such device is e.g. disclosed in Patent Application Ser. No. 436,282.
It is one of the main problems of such vertically adjustable devices to create without excessive force a sufficient clamping force to prevent an undesired rotation of the support tube and especially the vise supported thereon when a workpiece is worked e.g. filed. The present devices do not solve this problem